When to Plant Onion in Hilo, Hawaii (96721)
Location
Hilo, Hawaii
ZIP Code
96721
USDA Zone
12b
Last Frost
Friday, January 1, 2027
📅 Planting Calendar
Start Seeds Indoors Friday, November 6, 2026
Transplant Outdoors Friday, January 15, 2027
Pro Tip: Start Onion seeds indoors 8 weeks before your last frost date for best results.
🌿 Plant Details
Scientific Name Allium cepa
Days to Maturity 100 days
Mature Height 12-18"
Spread 4"
Type Bulb
Fruit Size Medium (2-4 inch bulb)
☀️ Growing Requirements
☀️
Sun
Full Sun (6+ hours)
💧
Water
Moderate
↔️
Spacing
4" apart
🌱
Planting Depth
0.5" deep
Seeds typically germinate in 7-10 days
🤝 Good Companions
CarrotBeetLettuceTomatoBrassicas
⚠️ Avoid Planting Near
BeanPeaAsparagus
Other Plants for Hilo
Blackberry Blueberry Raspberry Strawberry Basil Chamomile Chives Cilantro Dill Lavender Lemon Balm Marjoram Mint Oregano Parsley Rosemary Sage Tarragon Thyme Acorn Squash Artichoke Arugula Asparagus Beefsteak Tomato Beet Bell Pepper Bok Choy Broccoli Brussel Sprout Butternut Squash Cabbage Cantaloupe Carrot Cauliflower Cayenne Pepper Celery Cherry Tomato Chili Pepper Collard Green Common Bean Cucumber Eggplant Endive Fennel Garlic Grape Tomato Green Bean Habanero Pepper Head Lettuce Heirloom Tomato Honeydew Melon Jalapeño Pepper Kale Kohlrabi Leaf Lettuce Leek Lima Bean Mustard Okra Parsnip Pea Poblano Pepper Pole Pea Potato Pumpkin Radicchio Radish Rhubarb Roma Tomato Rutabaga Serrano Pepper Shallot Snap Pea Snow Pea Spaghetti Squash Spinach Squash Sweet Corn Sweet Potato Swiss Chard Tomato Turnip Watermelon Zucchini
Growing Onion in Zone 12b
Onion (Allium cepa) is a popular garden vegetable. In Hilo, Hawaii, which is in USDA Hardiness Zone 12b, you should start seeds indoors around Friday, November 6, 2026.
Your average last frost date is Friday, January 1, 2027. Plan to transplant your Onion seedlings outdoors around Friday, January 15, 2027, about 2 weeks after your last frost date.